1. Field of the Invention
The present invention relates to a method for generating areas of increased conductivity on the surface of a body of dielectric material, and in particular to a method for preparing the surface for connection of an electrode or other electrical interconnect to the area.
2. Description of the Prior Art
The use of electrical interconnections and/or electrode surfaces applied to bodies consisting of dielectric material, such as ceramic material, is well known. The use of brazing silver for this purpose is also known, this yielding electrically conductive layers having good adherence properties due to the composition of the brazing silver, particularly on metal oxide ceramic and crystalline material, particularly single-crystals.
Erosive working of material, particularly ceramic material, by means of laser radiation is also known. Drilling crystals for use as clock oscillators using laser radiation is described in U.S. Pat. No. 3,601,576. Such drilling may take place in oxidizing, reducing or neutral atmospheres, as needed. For processing ferrites, the laser radiation is used in a halomethane atmosphere, wherein the halogen portion is the determining factor for such etching.
Laser radiation has also been used for manufacturing low-impedance contacts on barium titanate. Such material must, however, be already in the form of semiconductive material in order to apply a metal contact having low electrical resistance thereto. Such a process is described in U.S. Pat. No. 4,261,764. The existing electrical conductivity of the semiconductive barium titanate is not changed by the application of such contacts.
Published European patent application No. 00 21 087 describes a method for producing electrical interconnects using laser radiation. As described therein, a body having a metal or alloy layer on a ceramic glass or silicon substrate is used. The metal or alloy layer has an amorphous structure and thus has little electrical conductivity. As a result of the applied laser radiation, a crystallization process takes place within the layer disposed above the substrate due to the heat of the laser radiation. This crystallization process permits the material of the metal or alloy layer to be converted from the amorphous into the coarse crystalline or single-crystalline state at the location of the laser radiation. The material of this layer has a higher conductivity in the crystalline state, so that electrical interconnects in such a layer, which is otherwise substantially electrically insulating, can be generated.
Perovskite oxide material is another important dielectric material, used in ceramic (polycrystalline) as well as single-crystal form. Barium titanate, strontium titanate, plumbous zirconate titanate as well as corresponding niobates, tantalates and the like are particularly useful in this regard. These materials are utilized in electronics as capacitor dielectric material, as piezo electric elements, and the like.